Method of and apparatus for controlling the refueling of coal stokers



Se t. 11, 1934. R. TEEPLE I 1,973,128

METHOD OF AND APPARATUS FOR CONTROLLING THE REFUELING 0F COAL STOKERS Filed April 28, 1934 1e 2 ,2 1;: 5 WMEN R H 10v 1; LJZTI'EEPLE I @E/W Patented Sept. 11, 1934 UNITED STATES METHOD OF AND APPARATUS FOR CON- TROLLINGL THE REFUELING OF COAL STOKERS Lawrence R. Teeple, Portland, Oreg.

Application April 28, 1934, Serial No. 722,961

Claims. (01. 236-9) This invention relates generally to coal stokers, and particularly to a method of and apparatus for controlling the refueling thereof.

The main object of this invention is the pro- 5 vision of an exceedingly simple apparatus which will cause the stoker to be operated merely for the purpose of maintaining a fire, regardless of temperatures at the point of delivery or storage, and in which a means is provided for preventing the operation of the periodic refueling or fire maintaining device until a reasonable length of time has elapsed following the previous operation of the stoker.

It is a commonly recognized fact that it is desirable to provide a means for maintaining a fire in connection with underfeed stokers during the extended intervals in which there have been no. calls for heat, which the Stoker normally supplies in responseto the ordinary form of controls, such as room thermostat with or without protective devices at the furnace or boiler.

In order to accomplish this refueling or firemaintaining it is customary to operate a stoker intermittently at periods which are determined solely by temperatures within the furnace or the furnace stack.

Still another method is to provide a time-controlled switch so arranged as to operate the stoker at each interval of time. That is to say,

in one class of devices the refueling is controlled by temperature at or near the furnace, and in the other form the refueling takes place on the time basis.

Each of these systems of controls contains certain advantages and disadvantages and it is the.

purpose of the present application to so combine certain of the elements thereof that by means of an exceedingly simple construction a fire will be positively maintained at all times by means of automatic refueling operations on a time basis, if and only when the temperature of the stack or other directly responsive part of the heating plant. falls to a. point which indicates that the fuel bed must be built up if the fire is to be maintained.

These, and other objects, will become more apparent from the specification following as illustrated in the accompanying drawing, in

which:

Fig. 1 is a front elevation of a timed refueling switch with portions of the front broken away to disclose the parts.

, Fig. 2 is a section taken along the line 2-2 in Fig. 1.

Fig. 3 is an enlarged view of the trip mechanism taken along the line 3-3 in Fig. 2.

Fig. 4 is a section taken along the line 4-4 in Fig. 1.

Fig. 5 is a diagrammatic view showing a simple form of the installation. Similar numbers of reference refer to similar parts throughout the several views.

Referring in detail to the drawing, there is shown a furnace 10 to which fuel is supplied from a hopper 11 by means of a motor 12. The furnace 10 is supplied with a smoke pipe 13 which discharges into a chimney 14. There is also shown the floor 15 of a room 16 in which is placed the room thermostat 1'7, one of whose leads 18 is connected to a power line 19 and the other lead 20 is connected to the motor 12, which is also connected to the power line 19.

For the purpose of simplifying the illustration a high voltage arrangement is shown, it being understood that when lower voltages are to be used suitable transformers, relays and other instruments may be employed such as are now in common use for similar purposes.

It will be noted that the heating plant and the room thermostat 17 will cause an increase in the amount of heat generated by the furnace 10 whenever the temperature of the room 16 falls below a predetermined minimum, and this would be fairly satisfactory without any other addition if there were constant demands for heat from the room 16, or at least that the intervals between the demands did not exceed the minimum period of time during which the fire would remain alive, or sufficiently so to be rekindled at the next closing of the thermostat 17.

The problem involved herein, however, is to maintain a fire in the furnace 10 during those periods of time in which there are no calls for heat from the room 16 or its equivalent.

To accomplish this I have shunted around the thermostat 1'7-that is, across the leads 18 and 20 and in series with each other, a timed refueling switch 21 and a simple stack thermostat 22 which, in this case, is illustrated as being adja-'- cent to the smoke pipe 13. The thermostat 22 may be similar in form to the thermostat 17, and its precise details will vary according to the particular element with which it is associated.

The timed refueling switch 21 includes a. pair of plates 23 and 24 which are separated by the pillars 25, and the plate 23 is supported from the base 26 by means of the pillars 27.

Secured to the plate 23 is a small electric timing motor 28 whose shaft 29 journals between the plates 23 and carries a pinion 30 which meshes with the gear 31. The gear 31 has attached thereto a pinion 32 which meshes with the gear 33. The gear 33 has attached thereto a pinion 34 which meshes with a'center wheel 35 which drives its shaft 36 through the friction spring 37. The shaft 36 carries on its outer end a dial 38 on which is movably mounted a trip 39.

The trip 39 has secured on the inner end thereof a cam 40 whose working face 41 is curved to provide a smooth working relationship with the trip pin 42, whose connections will be described later.

Mounted on the trip 39 is an arcuate arm 43 in whose slot 44 are placed the clamping screws 45,'by means of which the arm 43 may be held in a fixed relationship with the trip 39. An indicatcr point 46 projects from the arm 43 and poin s toward the calibrations 47 on the face of the trip 39.

Carried by the arm 43 is a second cam 43 whose working face 49' is curved. On the back of the trip 39 is an arm 50 which carries a clamping screw 51 which engages a groove 52 in the face ,of the dial 38.

By means of the screw 51 the entire trip 39 may be moved around to any desired position on the dial 38, and by means of the screws 45 the cam face'49 may be moved around to vary its relationship to the face 41.

The trip pin 42 is attached to a rocker arm 53 which is pivotally mounted on the standards 54. The rocker arm 53 carries a contact arm 55 of insulating material. Springs 56 urge the contact arm 55 to one side or the other of the arm 53, to which it is hinged. I

There is provided a spring contact arm '57 which engages the end of the arm 55 whenever the pin 42 is moved by the cam 40, thus closing the circuit as' far as the instrument 21 is concerned. If, however, the temperature at the smoke pipe 13 is high enough to hold the thermostat 22 open then no periodic refueling can take place, but when the temperature of the pipe 13 falls sufficiently to permit the stack thermostat 22 to close, then will commence a series of separate timed operations of the stoker until the temperature of the smoke pipe 13 rises sufilciently to open the thermostat 22.

It can be seen that by this construction, even though the stoker has been operated under its room thermostat control and has just ceased to operate, and that by a coincidence it happens to be timed for the switch 21 to close its portion of thelmotor circuit, refueling cannot take place until .thenext timed period which follows the closing of the stack thermostat 22 and, as stated,

this can only take place after a sufficient period of time has elapsed since the last stoker operation, not only to make a refueling action unobjectionable but also to make it necessary for the purpose of maintaining the fire.

' It can thus be seen that utilization is made of the fact that there is an appreciable lag in the time interval between the last normal operation of the stoker and the next timed interval of operation.

In Fig. 4 there is shown an additional contact I maintaining the fire when the temperature of a part which is directly responsive to the heating plant falls below a predetermined minimum.

2. A control for underfeed stokers having in combination a thermostatic control for operating the stoker in response to heat requirements, and an independent refueling device comprising a stack thermostat in series with a timed refueling switch forming a shunt around said first mentioned thermostat.

3. A control for underfeed stokers having in combination a timed refueling switch and a normally open stack thermostat in series therewith forming a part of a stoker motor-operating circuit whereby a subnormal temperature at the stack thermostat will cause its portion of the motor circuit to close, and the next following closing of the portion of the motor circuit represented by the timed refueling switch will cause said motor to be operated.

4. A control for underfeed stokers comprising a timed refueling switch whereby a portion of a circuit may be closed at periodic intervals, and a thermostat directly responsive to heat generated by the stoker in a manner toclose the second portion of the circuit when the tempera- 5. The combination of a stoker having a mo-- tor for operating same with a timed refueling switch for intermittently operating the stoker when the fire burns below a predetermined minimum, and a thermostat directly responsive to said fire and substantially independent of other.

temperature conditions interposed in the timed iso 

